This invention relates to a temperature responsive circuit especially, but not exclusively, suitable for controlling the operation of a power semiconductor device such as a power MOSFET.
EP-A-369530 describes a temperature responsive circuit comprising a temperature sensitive device, a first current source provided in series with the temperature sensitive device and detecting means having an output for providing a voltage signal which varies with the temperature sensed by the temperature sensitive device.
The circuit described in EP-A-369530, which corresponds to U.S. Pat. No. 5,039,878 (Aug. 13, 1991), is provided to determine whether the temperature of an active device, for example, a power semiconductor device in thermal contact with the temperature sensitive device, exceeds a predetermined threshold and to provide an output signal indicating when the predetermined threshold is exceeded.
The use of such temperature sensing circuits is of particular interest in the field of so-called `smart power` devices in which control functions provided by low voltage logic devices are integrated with power semiconductor devices such as power MOSFETs to provide intelligent power switches for use in high volume applications such as automotive control systems.
In certain overload conditions in such smart power devices, for example, where an overload of low resistance (say about 100 m.OMEGA. (milli-ohm) is present, the device is forced into a current-limiting mode. The power semiconductor device, generally a power MOSFET, will then dissipate power and heat up rapidly. Especially where the mounting base temperature of the smart power device is already high, then temperatures within the power MOSFET may quickly exceed safe operating limits.